1. Field of the Invention
This invention relates generally to electric connectors and particularly relates to a pin and pin socket connector having means for suppressing electromagnetic interference when the pin sockets are separated from the pins.
2. Description of the Prior Art
In order to protect sensitive electronic circuits from the effects of electromagnetic radiation, they are usually enclosed in a metallic shield. Such electromagnetic radiation or interference may be generated in the surrounding environment. When electromagnetic radiation is severe, such as aboard ships, aircraft or on land-based transmitter stations, where electromagnetic radiation emitters are in close proximity, the shields must be particularly well designed. They must be "radio-frequency tight". Sometimes they are doubled to insure that the circuit is properly isolated from high level radiation fields.
Generally, electronic circuits which are shielded in this manner must be permanently interconnected by wiring to other shielded enclosures which are necessary to the overall function of the system. These wires or cables in turn must also be shielded by metal-to-metal connections. Otherwise the required overall integrity of the shield cannot be maintained.
Instead of shielding the cables, it ahs also been proposed to filter each line or wire of the cable at the point it enters the shielded enclosure. The effectiveness of such a line filter, however, is limited. It depends very much on the termination impedance at the end of each line which is usually relatively low. In some systems there is a requirement to have temporary test connectors, for example at cable interconnect points. These test connectors must be accessible on the surface of a shielded enclosure. When these connectors are not in use, they are generally covered with a protective shield cap to maintain the shield integrity of the enclosure.
When a missile is launched, the umbilical connector between the missile and the launching station must be removed. This effectively leaves a hole or aperture in the missile skin which operates as a shield. Each open end wire at the open connector now functions as an antenna to pick off electromagnetic radiation. Missile launch generally takes place in an environment having severe electromagnetic disturbances. Furthermore, missile launch is a critical phase of the missile system where shielding is most essential. Filtering of each line or wire at the interface would be ineffective because after the umbilical connector is disconnected, the lines are open ended or not terminated. Hence they exhibit a very high impedance. It might be possible to provide automatically closing connector cover shields on the umbilical opening. However, they are difficult to design, costly to fabricate and install and if they do not work, they do not solve the problem.
The present invention makes use of certain properties of waveguides. That is each waveguide has an upper cutoff frequency and frequencies below cutoff are suppressed. this cutoff frequency suppression factor can be selected by the dimensions of the waveguide.
Many electrical connectors are known to the art. In some of these, an open space may surround the connector pins which would operate as a waveguide. Such an example is shown in the U.S. Pat. No. 3,825,874 to Peverill. This patent discloses an electrical connector where the pin contacts are mounted in open passages. Insulators are provided for the pin sockets. However, this patent does not discuss electromagnetic interference nor any solution for the avoidance of such interference.
Reference is also made to the U.S. Pat. No. 2,915,734 to Alden. FIGS. 4-6 of this patent show a shielded connector configuration of multiple female contacts. Shielding is provided between the various contacts by metallic inserts. Further, the U.S. Pat. No. 1,871,397 to Watts shows female contact pins or pin sockets, each being provided with an outer layer of insulation.